This invention relates generally to a liquid level system and, more particularly, to such a system employing an apparatus for detecting the level of liquid in a tank which is capable of operating at relatively high temperatures and pressures.
Reference is made to FIG. 18 of my U.S. Pat. No. 3,853,006 which discloses a liquid level system embodying a liquid level measuring apparatus comprising a pair of vertically spaced bellows mounted inside a tank and interconnected by a conduit. The two bellows and the conduit are filled with water or oil providing a reference column for the liquid level measuring apparatus. A transducer, such as a linear variable displacement transformer, is coupled to the lower bellows. The transducer produces an electrical output signal which is proportional to the difference between the pressures at the locations of the upper and lower bellows and, therefore, the level of water in the tank.
If the foregoing tank operates at very high temperatures and pressures, such as at 650.degree. F. and 2200 psi, and pressure is lost in the tank, the water or oil used as the reference column will become super-heated and vaporize, thereby causing the bellows to rupture and therefore rendering the liquid level measuring apparatus inoperative. It is the object of the present invention to overcome this shortcoming of the aforementioned liquid level measuring arrangement.